2.2 Ions & Ionic Bonds

• Ion

  An electrically charged atom or group of atoms formed by the loss or gain of electrons

  
• Ionic bonding

  The force of attraction between oppositely charged ions that holds ionic compounds together
• Formation of ions

  1. Atom loses or gains electrons to become more stable

  2. Electronic configuration of ion is the same as a noble gas

  
• Ionisation of metals and non-metals

  • Metals lose electrons to become positively charged cations
  • Non-metals gain electrons to become negatively charged anions

  
• Ionic compound

  • Formed when metal atoms react with non-metal atoms
  • Positive and negative ions held together by strong electrostatic forces of attraction
• Dot-and-cross diagrams

  • Show arrangement of valence-shell electrons
  • Only valence electrons shown
  • Charge of ion spread evenly and shown in brackets
  • Charge on each ion written at top right

  
• Lattice structure

  • Arrangement of atoms in 3D space in an ordered and repeating fashion
  • Ionic compounds have a giant lattice structure with alternating positive and negative ions
• Properties of ionic compounds

  • Usually solid at room temperature
  • Have high melting and boiling points
  • Good conductors of electricity in molten state or solution
  • Poor conductors in solid state